Methodology: The randomized, double blind, placebo-controlled pilot study used a crossover design. Ten subjects with refractory PTSD were assigned to one of two arms: one arm (n=5) received combined ketamine infusion and TIMBER therapy (TIMBER-K arm) and the second (n=5) received combined placebo (normal saline) infusion and TIMBER therapy (TIMBER-P arm). All 10 subjects received a short version of TIMBER therapy after 10 minutes of onset of the infusion in which reactivation of trauma memories was initiated in a controlled manner using standardized scales and scripted narrative of the index trauma. This was followed by a standardized mindfulness based cognitive therapy module to quickly de-escalate the arousal symptoms followed by induction of detached observation and reappraisal of the trauma experience. After completion of the 40-min infusion, all subjects were trained on the full version of TIMBER therapy using methods of mindfulness based graded exposure therapy and a twice-daily schedule of home practice was initiated. The investigators are currently in a process of recruiting fifty more subjects to examine the effects in a larger sample.